Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 15 2024 20:29:08 AWUS01 KWNH 152029 FFGMPD WIZ000-ILZ000-MNZ000-IAZ000-160230- Mesoscale Precipitation Discussion 0621 NWS Weather Prediction Center College Park MD 428 PM EDT Mon Jul 15 2024 Areas affected...Central & Eastern IA...Southwest WI...Northwest IL... Concerning...Heavy rainfall...Flash flooding likely Valid 152030Z - 160230Z SUMMARY...Another MCS traversing saturated ground conditions with rates of 2-2.5"/hr and 3-5" totals pose likely flash flooding, especially over E IA/S WI/N IL where rounds have overlapped the most over the last few days. DISCUSSION...GOES-E WV shows a broad longer wave cyclonic trough over the Upper Great Lakes and Western Ontario, another strong jet streak moving through central MN into the U.P. of Michigan with core around 90-100kts at 250mb. This places the area of concern within broad diffluent flow south of the jet core, but also with increasing divergence as the right entrance focuses across S MN into WI over the next few hours. In the low levels, a pre-frontal surface wave continues to deepen across west-central IA near CIN/FOD. A trailing pressure trough into SE NEB is acting as an effective cold front/surface convergence boundary...while a similar effective warm front exists east toward ALO to CWI and north of BMI/CMI and south of LAF. Winds are backed along this boundary and the pooling moisture (in the upper 70s to low 80s) and ample insolation has resulted in an enhanced cu field. MLCAPE of 4000-4500 J/kg is analyzed along the boundary with slowly eroding capping. Similarly, deep layer moisture/TPW values are pooling too at or just above 2" through depth. Stronger low level convergence near the low and upper-level jet ascent is resulting in convective initiation upstream near the front. Cells will be capable of 2-2.5"/hr rates, though initial deep layer steering flow is likely to result in fast forward propagation to mitigate higher totals in the short-term. However, as CAPE continues to increase downstream, southwesterly LLJ will increase from 15-20kts to 25-30kts increasing convergence and resulting in cells further down the effective warm front developing. Initially slower, these stage setting cells, will remain orientated parallel to the deeper layer flow as organization and upscale growth occurs into a stronger MCS/squall line. As such, spots of 2-3" with a secondary 2" in a sub-hourly manner should result in spots of 3-5" across E IA into NW IL. Additionally, as the LLJ strengthens from the southwest, this is more orthogonal to the effective front and spots where boundary layer/surface based pre-cursory cells do not develop, should isentropically ascend resulting in elevated speed convergence and convective initiation across NE IA/SW WI, expanding the areas of intense rainfall. Given these areas also have seen recent heavy rainfall; grounds are 65-80% saturated through 40cm per NASA SPoRT LIS products and FFGs are below 2.5"/3hrs (even lower across the S WI/N IL two rows of border counties). As a result, flash flooding is considered likely (especially after 00z) with some considerable flash flooding possible, especially in/near urban centers like Rockford, IL, Dubuque, IA, the Quad Cities and Madison, WI and eventually the NW Suburbs of Chicago in the early overnight period.=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_zKR9cECaINb0_grsHuFI4PSFymHYuYMY8b2Y46EdUdlho9MQdtgd_Y36mg9aJNmtjtQ= _z4BlMn1A9436-rEx4LeU0k$ for graphic product... ATTN...WFO...ARX...DMX...DVN...ILX...LOT...MKX... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 43679009 43458890 42408826 41268832 40568925=20 40699083 41099279 41479415 41759496 42449509=20 43099333 43579150=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .